Electric furnace



Sept. 6,1927. 1,641,764

' w. J. KEENAN ELECTRIC FURNACE Fiied Feb. 26, 1927 Inventor: William .J. Keenan His Afterneg.

UNITED STATES 1,641,764 PATENT OFFICE.

\ WILLIAM J. KEENAN, OF SCHENECTADY, NEW YORK, ASSIGNOR. TO GENERAL ELECTRIC COMPANY, CORPORATION OF NEW YORK.

ELECTRIC FURNACE.

' Application filed February 26, 1927. Serial No. 171,297.

My invention relates to electric furnaces and has for its object the provision of a simple and rugged heating resistor for electric furnaces. i

In carrying out my invention I provide recesses in the furnace wall in opposite sides ofthe heating chamber and heating elements consisting of bars extending across the heating chamber and having their ends lying in said recesses. I also providespacing members for the bars, which members are secured in the recesses and some of which may be electric insulators whereby the bars areconnected together into series or parallelrelation to form a heating resistor for the furnace.

' For a more complete understanding of my invention reference should be had to the accompanying drawing in which Fig. 1 is a fragmentaryview in vertical section of an electric furnace embodying my invention; Fig. 2 is a fragmentary sectional view taken along line 22 of Fig. 1, looking in the direction of the arrows; while Fig. 3 is a horizontal sectional view on a reduced scale showing the arrangement of the heating resistor.

Referring to the drawing, I have shown my invention in one form as applied to an electric furnace provided with heat refractory walls 10 enclosing a heating chamber '11. This wall may be and preferably is formed of heat refractory bricks. Near the top of the heating chamber specially formed secured to the wall at opposite sides of the heating chamber.' As shown, these special bricks 12 are built into the wall in two horizontal rows at opposite sides of the heating chamber. Preferably, the two rows are coextensive with the particular-walls in which they are placed, for example, they will extend from the front to the back of the furnace. The bricks are each provided with a recess 13 which in the form shown consists of an inner cylindrical opening 13 extending'horiz ontally and parallel with the furnace wall and an outer' slot 13 communieating therewith and also extending horizontally, but having a smaller dimension in a vertical direction. The special bricks being placed inend to end relation with their recesses registering thus provide two recesses in opposite walls of the heating chamber.

The heating resistor'is made up of a plubricks-12, forming supporting members, are.

rality of bars 14, made of a suitable resist- I ance heating material, which are shown as being cylindrical in form. These bars are preferably made of a mixture of material comprising a base material of silicon carbide with an inner mixture of graphite, calcium carbide and oxides of iron, such as disclosed, for example, in Patent No. 1,420,980, to'Eichenberger, dated June 27, 1922. The bars have their ends extending into the recesses 13 whereby they are supported in the heating chamber. Spacing members 15 for the bars are also provided in the recesses. These Spacing members are cylindrical inform so as to loosely fit into the inner portion of the I recess 13 and are provided with grooves at their ends in which the bars are received and secured between two adjacent spacing mem berg. The spacing members also serve the purpose of establishing an electrical connection with the bars. bers of electrically conducting material, and suitably locating the supply terminals, the bars may be connected in parallel while by using alternate spacing members of insulating material, as shown in the drawing, the bars are connected in series.

In the arrangement shown, with an even number of bars connected in series, the electrical connections for the two ends of the resistor are made on the same side of the furnace. A terminal memberv 17 is provided. at one end of the recess in electrical connec- By using spacing memtionwith a conducting spacing member 18.

the end spacing member 2. This spacing 1 member, however, is forced inward by a helical spring 22 whereby the series of bars and the spacing members are secured" together and a good electrical contact maintainedbetween them. A terminal 23 is provided having an enlarged inner end in engagement with the spacing member '21 and of substantiallythe same size as the spacing member. A smaller portion of the terminal extends outward through the. helical spring 22 and the spring is seated on the shoulder 24 thereby formed. The outer end of-.the spring bears against an adjusting nut 25' secured in a bracket 26 whereby the tension of the spring can be adjusted. A central bore is provided the nut 25 for the terminal, this bore being provided with an insulating bushing 27. It will be noted that the outer ends of the spacing members 18' and 21 are convex and fit in the concaved inner ends of the terminals 17 and 23. The

pressure applied by the spring 22 forms a good electrical contact at these contacting surfaces as well as between the various spacing members and the resistor bars 14. As shown in Fig. 3, the spacing members on the opposite side of the furnace are held ingood electrically conducting relation with the ends of the bars by means of a spring 28.

The spacing members may bemade of any suitable insulating or conducting materials as the case maybe. The conducting spacing members may be made of the same material as the resistor bars but containing a greater amount of iron oxide to increase its conductivity, while the insulating spacing members may be made of an aluminumoxide composition.

While I have described my invention as embodied in concrete form and as operating in a specific manner in accordance with the provisions of the patent statutes, it should be understood that I do not limit my invention thereto since various modifications thereof will suggest themselves to those skilled in the art without departing from the spirit of my invention the scope of which is set forth in the annexed claims.

lVhat I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric furnace comprising heat refractory walls forming a heating chamber, supporting members provided with recesses secured to said walls on opposite sides of said chamber, bars forming heating elements extending across said heating chamber having their ends lying in said recesses, and electrically conducting spacing members for said bars in said recesses whereby said bars are electrically connected together to form a heating resistor.

2. An electric furnace comprising heat refractory Walls forming a heating chamber,

s'upportingmembers provided with recesses secured to opposite sides of said chamber, bars forming heating elements extending across said heating chamber having their ends lying in said recesses, electricallyconducting spacing members for said bars in said recesses whereby said bars are electrically connected together to form a heating resistor, and yieldable means for holding said spacing members and said bars in electrically conducting relation.

7 Patent No. i 1,641,764..

a WILLIAMJpKEENAN;

3. An electric furnace comprising heat refractory walls forming a heating chamber, supporting members provided with recesses secured to opposite sides of said chamber, bars forming heating elements extending across said heating chamber having their ends extending into said recesses and alternately arranged conducting and insulating spacing members for said bars in said recesses whereby said bars are electrically connected together to form a heating resistance.

4. An electric furnace comprising heat refractory walls forming a heating chamber, supporting members secured to said walls on opposite sides of said chamber, bars forming heating elements extending across said chamber having their ends resting on said supporting members, spacing members for said bars on said supporting members, at least part of said spacing members being electrically conducting, and resilient means for holding said spacing members and bars together in good electrically conducting relation.

5. An electric furnace comprising heat refractory walls forming a heating chamber, supporting members secured to said walls on opposite sides of said chamber, said supporting members being provided with recesses, bars of carbonaceous material forming heating elements extending across said chamber having theirends lying in said recesses, spacing members for said bars in said recesses, at least' part of said members being electrically conducting, and resilient means for holding said spacing members and bars together in good electrically conducting relation.

6. An electric furnace comprising heat refractory walls forming a heating chamber, heat refractory-electrically insulating sup- 1 0 porting members built into said walls at opposite sides of said heating chamber, said members being provided with horizontal recesses, bars of carbonaceous material forming heating elements extending across said heating chamber and having their ends lying in said recesses, spacing members for said bars in said recesses, at least part of said spacing members being electrically conducting whereby said bars are connected together to form a heating resistor, and resilient means for holding said spacing members and bars together in good electrically conducting relation.

In witness whereof I have hereunto set my hand this 24th day of February 1927.

WILLIAM J. KEENAN.

c Certifiat'of Correction.

Granted September 6, 1927, to

It is hereby certified that error appears in the printed specification of the; abovenumbered patent requiring correctionas follows: Page 1. line 95, for the numeral 2 read 21', and that the said Letters Patent should be read with this correction therein that the same may conform to the recordof the case in the Patent Oflice.

Signed andsealed this 18th day of October, A. D. 1927.

M.'J. Moons '7 Acting Oomzmiasiomr of Patents. 

